This set of Manufacturing Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Expendable Mold, Expendable-Pattern Processes”.
1. Which of the following casting process uses a polystyrene pattern?
a) investment casting
b) ceramic-shell casting
c) evaporative-pattern casting
d) slush casting
View Answer
Explanation: The evaporative-pattern casting process uses a polystyrene pattern, which evaporates upon contact with molten metal to form a cavity for the casting. This process is also known as lost-foam casting and falls under the trade name full-mold process.
2. Which of the following casting process is used to make typical parts such as gears, cams, valves, etc?
a) investment casting
b) ceramic-shell casting
c) evaporative-pattern casting
d) slush casting
View Answer
Explanation: The investment-casting process, also called the lost-wax process, was first used during the period from 4000 to 3000 B.C. Typical parts made are components for office equipment, as well as mechanical components such as gears, cams, valves, and ratchets.
3. In which of the following casting, two halves of a mold are made from materials with high resistance?
a) investment casting
b) permanent-mold casting
c) evaporative-pattern casting
d) slush casting
View Answer
Explanation: In permanent-mold casting (also called hard-mold casting), two halves of a mold are made from materials with high resistance to erosion and thermal fatigue, such as cast iron, steel, bronze, graphite, or refractory metal alloys.
4. To increase the life of permanent molds, the surfaces of the mold cavity usually are coated with a ____________
a) refractory slurry
b) silver
c) aluminum
d) zinc
View Answer
Explanation: In order to increase the life of permanent molds, the surfaces of the mold cavity usually are coated with a refractory slurry (such as sodium silicate and clay) or sprayed with graphite every few castings. These coatings also serve as parting agents and as thermal barriers, thus controlling the rate of cooling of the casting.
5. Which of the following casting technique is an alternative to investment, shell-mold, and green-sand casting?
a) Vacuum Casting
b) Permanent-mold casting
c) Evaporative-pattern casting
d) Expandable-mold casting
View Answer
Explanation: Vacuum casting is an alternative to investment, shell-mold, and green-sand casting and is suitable particularly for thin-walled (0.75 mm) complex shapes with uniform properties.
6. Hollow castings with thin walls can be made by permanent-mold casting using ___________
a) vacuum casting
b) slush casting
c) evaporative-pattern casting
d) investment casting
View Answer
Explanation: Hollow castings with thin walls can be made by permanent-mold casting using this principle: a process called slush casting. This process is suitable for small production runs and generally is used for making ornamental and decorative objects (such as lamp bases and stems) and toys from low-melting-point metals such as zinc, tin, and lead alloys.
7. In which of the following casting technique, the molten metal is forced upward by gas pressure into a graphite or metal mold?
a) vacuum casting
b) slush casting
c) pressure casting
d) investment casting
View Answer
Explanation: In pressure casting (also called pressure pouring or liquid pressure casting), the molten metal is forced upward by gas pressure into a graphite or metal mold.
8. Which of the following are made of two or more different materials?
a) Composite molds
b) Centrifuging
c) Die casting
d) Investment casting
View Answer
Explanation: Composite molds are made of two or more different materials and are used in shell molding and other casting processes. They generally are employed in casting complex shapes, such as impellers for turbines.
9. In which of the following casting technique, the metal is heated to just above its solidus temperature and poured into a vessel to cool it down to the semisolid state?
a) vacuum casting
b) rheocasting
c) pressure casting
d) investment casting
View Answer
Explanation: In rheocasting, the metal is heated to just above its solidus temperature and poured into a vessel to cool it down to the semisolid state. The slurry is then mixed and delivered to the mold or die.
10. The advantages of semisolid metal forming over die casting are _____________
a) the structures developed are homogeneous, with uniform properties
b) casting as well as wrought alloys can be used
c) the lower superheat results in shorter cycle times
d) all of the mentioned
View Answer
Explanation: The advantages of semisolid metal forming over die casting are
a) the structures developed are homogeneous, with uniform properties, lower porosity, and high strength
b) both thin and thick parts can be made
c) casting as well as wrought alloys can be used
d) parts subsequently can be heat treated,
e) the lower superheat results in shorter cycle times.
However, material and overall costs are higher than those for die casting.
Sanfoundry Global Education & Learning Series – Manufacturing Engineering.
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